Gas turbine arrangement



March 6, 1945. c. w. SMITH GAS TURBINE ARRANGEMENT Filed Sept. 17, 1941 F L24 SLIP? 7395/) lnventor" Chester W.Sm

-Acicorvrwey. I

Patented Mar. 6, 1945 i UNITED "STATES, PATENT. ,o-FFICE' I GAS TURBINEARRANGEMENT Chester W. Smith, Lynn, Mass, assignor to Gen eral Electric Company, a corporation of New York Application September 17, 1941, Serial N6. 411,215

fe Claims. -(c1. 6041) The present. application is a continuation in part of my application Serial No. 281,562, filed June 28, 1939.

The invention relates to gas turbine arrange ments wherein a turbine has a bucket wheel so located that the exhaust gases issuing from the turbine buckets may sweep across the face of the wheel, or where one or more wheels are exposed to a current of air from the atmosphere or other source which furnishes oxygen for combustion of unburned fuel contained in the gases issuing from the wheel. The invention is of particular significance in connection with aircraft arrangements in'which an axial flow gas turbine wheel is secured to an overhung shaft portion with its outlet side substantially exposed to the atmosphere and having a surface. substantially parallel to the slipstream of the aircraft. Insuch an ar-v vention, as shown in Figs. 1 and 2, comprises a bucket wheel I ll which'has a central solid disk It forming .a rim l2 and a row of buckets l3 secured to the rim I2. Theouter ends of the buckets 13 are connected by -a band or shroud The bucket wheel is secured to an overhung shaft l5 supported on a bearing I6. An annular nozzle box l1 having a row of blades .18 forming nozzles between them is arranged to supply op-.

erating gas to the bucket wheel. The nozzle box has aninlet conduit 19 for connection to a suitable source of supply, such as the manifold of a combustioncnginanot shown. A partition or heat-insulating wall 20 is provided between the nozzle box l1 and the-bearing Hi to reduce heat transfer from the nozzle box to the bearing. in aircraft such gas turbine may serve to drive a.

- supercharger ora generator.

In many installations the 'turbineis-mounted so that the front surface of the bucket wheel is substantially parallel to the direction of the slip,v

stream as indicated by an arrow 2| in the drawing. The direction of the gases issuing from-the bucket wheel, as indicated by another arrow '22, is substantially perpendicular-to the direction ofthe slipstream. With regard to the slipstream, the upper portion of the bucket wheel in the drawing constitutes a leading portion or edge and the lower portion of the bucket wheel con stitutes a trailing portion or edge. I

The heating of the bucket wheel disk by gases discharged from the bucket wheel is considerproximity thereto and the. other cause is due to the slipstream which forces gases issued from the nozzles and buckets on theupstream side'of the bucket wheel towards the central portion thereof.

The object of my invention is toprovide im-' proved constructions and arrangements whereby excessive heating of a gas turbine of the type above described is prevented. This is accomplished in accordance with my invention by an arrangement in which the aforementioned causes are substantially eliminated.

For a better understanding of what 'I believe to be novel and my invention, attention is directed to the followin -description and the claims appended thereto in connection with the accompanying drawing. I

Inthe drawing Fig. 1 illustrates a sectional view of a gas turbine arrangement embodying my invention; Fig. 2 is a front view of Fig. l; and Figs. 3 and 4 are modifications in accordance with my invention.

A gas turbine arrangement according to my inably reduced in accordance with my invention by the provision of a cap or cooling device 23 ar-' ranged adjacent the bucket wheel. In the present instance the cap is concave-shaped with a rim bent inward and closely spaced with the adjacent surface of the bucket wheel disk, the spacing from the disk increasing towards the center of the cap. With the provision of such protectin cap, only a small amount, if any, of the gas issued from the bucket wheel will be forced through the.

clearance between the cap and the bucket wheel while the major portion of the gas issued from' the leading portion of the bucket-wheel is con-' ducted along the outer surface of the cap to the atmosphere.

Gases forced towards the cap 23 may cause heating of the latter but do not directly heat the bucket wheel as would be the case were no cap provided. Thus, the cap constitutes a device for protecting the bucket wheel disk from the heat of the gases issued from the bucket wheel.

In the present example, the cooling cap formed by inner and outer substantially uniform- Y boxl'l.

1y spaced walls 28' and 2] sealed together along their outer edges and forming a space 28 between them. Cooling air is conducted to the space 2' by means of an inlet conduit 29 connected to an opening 31! in the outer wall 21 and arranged to receive cooling air from any suitable source,

preferably from the slipstream. The cooling air is discharged from-the space 28 through an outlet conduit 3| connected-$ an opening 32 in the outer wall 21 diametrically across the opening 3|.

leading portions of the bucket wheel and the cap 52 areenclosed by a shield 58 to form a and the cooling air passed through the cap carries away a substantial amount of heat radiated towards the cap.

The leading half of the bucket wheel and the leading or upper portion of the cooling cap or device are enclosed'or shielded by a semi-annular shield 35 to form a smooth discharge passage for the gases discharged from the leading portion of the wheel and to prevent these gases from mixing with air in proximity to the leading portion of the wheel. The shield 85 has an outer flanged portion 36 fastened and sealed to the nozzle box by means including studs 31 and bolts 38. The shield, as stated above, covers about one-half of the bucket wheel and is spaced therefrom to form a channel 32 for smoothly discharging the gases in downward direction or, with reference to an aircraft, in rearward direction. During operation no air enters the channel 39 so that after-burning within the channel is reduced to a minimum. In addition, the shield 35 acts as a deflector for the slipstream, thus preventing the gases issuing from the bucket wheel from being forced with great intensity to-# wards the leading portion of the cooling cap.

The inlet conduit 29 'of the cap projects smooth discharge channel 59 for the gases discharged from the leading portion of the bucket wheel'and. to prevent the slipstream from forcing these gases towards the leading portion of the cooling *cap. The shield 58 comprises a semiapnular metallic ring 60 curved incross-section and having an edge portion in sealing contact with the casing of the nozzle box 50 and secured to ear 5! on the nozzle box by bolts 62. The semi-annular ring '60 is concentrically spaced with the bucket wheel. The shield includes another semi-annular. ring 63 of transparent heat resistant material'supported on the inner edge of the ring ,8! by means of a supporting member 54. The ring or, that is, the part of the shield towards which the main radiation from the i transparent to infra-red radiation.

bucket wheel takes place, is made from quartz, flint glass or like heat resistant material which The 1 transparent ring 53 during operation of the turbine promotes radiation of heat from the bucket wheel, in particular the buckets thereof, and

thereby reduces the temperature and accordingly weakening of the buckets.

The gas turbine arrangement shown in Fig. 4

comprises a bucket wheel 10 having an annular row or buckets H corresponding to the buckets through an opening 40 of the shield 35 and is supported thereon'and sealed thereto by a weld Thus the semi-annular shield covering the 4 l leading portion of the bucket wheel and the cooling cap also acts as a support for'the latter. The cap isadditionally supportedby a bracket 3 l2 securing the outlet conduit 3| The gas turbine arrangement shown in Fig. 3

to the nozzle ducting gases to the wheel, a device for preventil inrFlgs. 1 and 2. The leading portion of the wheel I. is substantially enclosed by a shield I2 similar to the shield '85 in Figs. 1 and 2 except that the shield 12 is provided with openings or perforations I3 opposite thev discharge. passages formed by and in axial alignment with the buckets ll. These openings permit. heat radiation from the buckets ll into the atmosphere during .operation. Little, if any, gases discharged from I thebucket passages pass through the perforations 15 because the'gases discharge from the bucket. passages at an angle toward the axial direction and are readily carried downward in v the direction of the slip stream shield 12. 7

What I claim as new and desire underneath the to secure by Letters Patent of the United States is:

1. Gas turbine arrangement for aircraft comprising a turbine wheel, a nozzle box for concomprises a, nozzle box corresponding to the box I! of Fig. 1 for conducting gases to a bucket. wheel 51 having an axis of. rotation substantially perpendicular to the direction of the slipstream. The central portion or an: of the buck et wheel i protected by a cooling cap 52 includ-i ing an. innendisk 52 and anouterdisk 5 with be'nt rim portions suitably secured and sealed together. The cooling air fromthe slipstream is conducted to the leading portion of the cap by an inlet conduit 55 and discharged from the cap by a discharge conduit 58 having an opening racing in the direction of the slipstream. A central portion 51 of'the outer'disk 541s dishedin or indented and closely spaced with or engaging the inner disk II. This dished-in portion 51 of the outer disk is broadly constitutes a baf-' fie to prevent cooling air received from the inlet conduit 55 from flowing directly along a diameter to the outlet conduit '58. Thus, the dishedin portion causes the cooling air conducted to the outer portion uniformly radially spaced from the bucket wheel with one edge sealed to thenozzle ing heating of the turbine wheel by the gases issuing therefrom comprising a hollow cap concave-shaped towards the outlet side of the wheel and having a rim closely spaced with the wheel and'inlet and outlet conduits for cooling medium connected to diametrically opposite portions of the cap, and a semi-annular shield having an box and a semi-annular member supported on the other edge and made of material transparent to heat radiation from the bucket wheel.

prising a turbine wheel with a row of buckets.-

wheel and to form a discharge channel for gases issuing from the wheel, said means comprising a hollow cap having inner and outer substantially parallel walls sealed along their rims and concave-shaped towards the central portion 01'. the bucket wheel, substantially aligned inlet and out-; let conduits connected to diametrically opposite.

portions of the cap, and a semi-annular shield sealed to the nozzle box and enclosing a portion I only oi-the bucket wheel and the cap, said shield 2. Gas turbine arrangement for aircraft com au ios 4Q r i having a portionciacing the buckets madetrom transparent material.

3.- A cooling cap ior gas turbine bucket wheels 'having an inner concave-shaped wa11..-an outer concave-shaped wall sealed to the inner wall and having a central indented portion eng sins the inner wall, and inlet and outlet conduits con'- nected to diametrically opposite portions of the outer'wall. a

a 4. In a ,gas turbine arrangement for aircraft comprising a bucket wheel'for rotation about an axis perpendicular to the direction of the slipstream, a. nozzle box located on one side oi. the wheel and ashield located on the other side of the wheel to prevent the slipstream from forcing gases issuing from the leading portion or the of the wheel, said shield having pertorations in axialalignment with the bucketsto permit ireeheat radiation therefrom into the atmosphere.

wheel towards the central portion thereof,- said shield being sealed to the nozzle .box and enclos ingthe leading portion only of the wheel, a portion 01' the shield being made of material transparent to heat radiation from the bucket wheel.

- 6. Ashield .ior gas turbine bucket wheels-discharging directly into the atmosphere, said'shield comprising a semi-annular ring curvedin crosssection, and another semi-annular ring made of heat resistant material transparent to infra-red radiation, and means securing the other-ring on the inner edge of the'first mentionedring. 

